This invention relates, in general, to evaluating the integrity of semiconductor metal structures, and more particularly, to measurement techniques for detecting defects in semiconductor metal structures.
During semiconductor manufacturing, defects can occur in the semiconductor's metal structures which, if undetected, can eventually result in malfunctions or complete failure of the manufactured product. Defects can result from a variety of sources including malfunctioning or misaligned equipment, particulates on the semiconductor material, residues remaining on the semiconductor material from previous manufacturing steps, and various other sources. With the increasing emphasis on quality in the manufacturing of semiconductor devices, manufacturing procedures generally include inspections for determining the presence of defects in conductive lines. Measurement techniques used to perform these inspections include SEM (scanning electron microscope) views of semiconductor surfaces, or cross sections; and thermal wave measurement techniques.
SEM surface photographs limit evaluations to semiconductor surface metalization features. SEM analysis of multi-layer metal system subsurface features requires SEM photographs of the metal structure's cross section. Although this technique provides detailed information concerning the semiconductor's structure, it has the disadvantage of being destructive since it requires slicing the die to expose the cross sectional view. Another disadvantage of the SEM analysis technique is the time required to prepare and analyze the many SEM photographs needed to adequately represent an entire semiconductor. These disadvantages, the time required to complete examinations and the destruction resulting from cross sectioning, have limited the use of SEM analysis as a tool for detecting defects during semiconductor manufacturing.
Thermal wave measurement analysis, which employs heating a semiconductor die with lasers then measuring the resulting thermal vibrations of the material's lattice structure, can also be used in detecting defects. As with SEM analysis, this technique also requires several views to represent an entire semiconductor and considerable time for analysis. Other disadvantages of thermal wave analysis are the resolution decrease associated with increased defect depth into the material, and high equipment cost.
Accordingly it would be desirable to have a nondestructive, rapid, and inexpensive method of detecting the presence of defects in semiconductor conductive lines that overcomes the problems of previous detection techniques.